No one will check this (Maeli really don't have the time to do so), so you can write in whatever language you want. Beut keep in mind that there are foreign players, so English is a good choice to be understood.

Perfect english is not important. But using english is! I suddently found myself in the House Hommel, and no-one writes english there at all. I know only a few german words, and I feel really isolated!

Most of the non-german players even do not look in the forum, even in the english ones..so most people, mostly german, write german... anyone who says he does not understand will get a translation i think, and if there are more activ international people, especially in the forum, more and more people write english.

If all the germans write english, the one does some mistakes, the other one who reads it misunderstoods something and there not one 'only' english player who reads it, it is not practible to write english.